My favorite quest was Blue's. Blue was a magician and in his quest you had to master all the magic in the game; to do this you had complete rein (reign? Either could work) in the open world so long as you got the magic. Magic in the game was a bunch of opposing elements, like you could decide to use either fire or ice magic, all very Yin and Yang. You eventually had to fight the "shadow" version of yourself -- using fire magic instead of ice, and, ultimately, space versus time magic -- but the game moves forward whether you win or lose that battle. If you win, you go on as Blue; if you lose you play as your shadow from then on. I think the only difference between them was the name and the sprite: either absorbed all the magic of the other (so they were the only characters to use both fire and ice magic).
So in addition to the open world (with no idea where to go) was the battle system. Like in FF2 (Japanese) the monsters got stronger as you got stronger, and some areas had stronger monsters than others. All this is to say, some areas of the game were absolutely killer, the hardest (superlative) I've ever come across in an RPG. Also, building skills and abilities was basically dumb luck, as you gained new attacks by fighting monsters: sometimes you'd attack and you would perform a new move. Fighting harder monsters seemed to build these faster.
There were also races with different skills. Mutants could absorb different skills from the enemies, used against them; there were monster characters that could join your party, too.
All this is to say, it's a confusing, light-on-story game with a diverse, sprawling, highly non-linear world, and how well you liked exploring that world -- and the intricate wider universe -- largely decided how much you liked the game. Basically it was as far from FF7 or whatever as you could get.